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Stewart JM. RNA nanotechnology on the horizon: Self-assembly, chemical modifications, and functional applications. Curr Opin Chem Biol 2024; 81:102479. [PMID: 38889473 DOI: 10.1016/j.cbpa.2024.102479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Revised: 05/20/2024] [Accepted: 05/25/2024] [Indexed: 06/20/2024]
Abstract
RNA nanotechnology harnesses the unique chemical and structural properties of RNA to build nanoassemblies and supramolecular structures with dynamic and functional capabilities. This review focuses on design and assembly approaches to building RNA structures, the RNA chemical modifications used to enhance stability and functionality, and modern-day applications in therapeutics, biosensing, and bioimaging.
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2
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Park SV, Kang B, Lee M, Yoo H, Jo H, Woo S, Oh SS. In vitro selection of a trans aptamer complex for target-responsive fluorescence activation. Anal Chim Acta 2024; 1301:342465. [PMID: 38553123 DOI: 10.1016/j.aca.2024.342465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 02/23/2024] [Accepted: 03/10/2024] [Indexed: 04/02/2024]
Abstract
BACKGROUND Most biological molecular complexes consist of multiple functional domains, yet rationally constructing such multifunctional complexes is challenging. Aptamers, the nucleic acid-based functional molecules, can perform multiple tasks including target recognition, conformational changes, and enzymatic activities, while being chemically synthesizable and tunable, and thus provide a basis for engineering enhanced functionalities through combination of multiple units. However, the conventional approach of simply combining aptamer units in a serial manner is susceptible to undesired crosstalk or interference between the aptamer units and to false interactions with non-target molecules; besides, the approach would require additional mechanisms to separate the units if they are desired to function independently. It is clearly a challenge to develop multi-aptamer complexes that preserve independent functions of each unit while avoiding undesired interference and non-specific interactions. RESULTS By directly in vitro selecting a 'trans' aptamer complex, we demonstrate that one aptamer unit ('utility module') can remain hidden or 'inactive' until a target analyte triggers the other unit ('sensing module') and separates the two aptamers. Since the operation of the utility module occurs free from the sensing module, unnecessary crosstalk between the two units can be avoided. Because the utility module is kept inactive until separated from the complex, non-specific interactions of the hidden module with noncognate targets can be naturally prevented. In our demonstration, the sensing module was selected to detect serotonin, a clinically important neurotransmitter, and the target-binding-induced structure-switching of the sensing module reveals and activates the utility module that turns on a fluorescence signal. The aptamer complex exhibited a moderately high affinity and an excellent specificity for serotonin with ∼16-fold discrimination against common neurotransmitter molecules, and displayed strong robustness to perturbations in the design, disallowing nonspecific reactions against various challenges. SIGNIFICANCE This work represents the first example of a trans aptamer complex that was in vitro selected de novo. The trans aptamer complex selected by our strategy does not require chemical modifications or immediate optimization processes to function, because the complex is directly selected to perform desired functions. This strategy should be applicable to a wide range of functional nucleic acid moieties, which will open up diverse applications in biosensing and molecular therapeutics.
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Affiliation(s)
- Soyeon V Park
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, South Korea
| | - Byunghwa Kang
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, South Korea
| | - Minjong Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, South Korea
| | - Hyebin Yoo
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, South Korea
| | - Hyesung Jo
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, South Korea
| | - Sungwook Woo
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, South Korea.
| | - Seung Soo Oh
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 37673, South Korea.
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3
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Chen W, Zhao X, Yang N, Li X. Single mRNA Imaging with Fluorogenic RNA Aptamers and Small-molecule Fluorophores. Angew Chem Int Ed Engl 2023; 62:e202209813. [PMID: 36420710 DOI: 10.1002/anie.202209813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 11/07/2022] [Accepted: 11/24/2022] [Indexed: 11/25/2022]
Abstract
Messenger RNA (mRNA) is the fundamental information transfer system in the cell. Tracking single mRNA from transcription to degradation with fluorescent probes provides spatiotemporal information in cells about how the genetic information is transferred from DNA to proteins. The traditional single mRNA imaging approach utilizes RNA hairpins (e.g. MS2) and tethered fluorescent protein as probes. As an exciting alternative, RNA aptamers: small-molecule fluorophores (SFs) systems have emerged as novel single mRNA imaging probes since 2019, exhibiting several advantages including fluorogenic ability and minimal perturbation. This review summarizes all five reported RNA aptamers: SFs systems for single mRNA imaging in living cells so far. It also discusses the challenges and provides prospects for single mRNA imaging applications. This review is expected to inspire researchers to develop RNA aptamers: SFs systems for studying gene expression at single-molecule resolution in cells.
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Affiliation(s)
- Wei Chen
- Institute of Cytology and Genetics, the Hengyang Key Laboratory of Cellular Stress Biology, Hengyang Medical School, University of South China, Hengyang, Hunan, 421001, China.,Beijing Institutes of Life Science, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Science, Beijing, 100101, China
| | - Xiaoying Zhao
- College of Chemistry and Materials Engineering, Beijing Technology and Business University, Beijing, 100048, China
| | - Nanyang Yang
- Institute of Cytology and Genetics, the Hengyang Key Laboratory of Cellular Stress Biology, Hengyang Medical School, University of South China, Hengyang, Hunan, 421001, China
| | - Xing Li
- Beijing Institutes of Life Science, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Science, Beijing, 100101, China
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4
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Hou Q, Jaffrey SR. Synthetic biology tools to promote the folding and function of RNA aptamers in mammalian cells. RNA Biol 2023; 20:198-206. [PMID: 37129556 PMCID: PMC10155629 DOI: 10.1080/15476286.2023.2206248] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 03/15/2023] [Accepted: 04/18/2023] [Indexed: 05/03/2023] Open
Abstract
RNA aptamers are structured RNAs that can bind to diverse ligands, including proteins, metabolites, and other small molecules. RNA aptamers are widely used as in vitro affinity reagents. However, RNA aptamers have not been highly successful as bioactive intracellular molecules that can bind target molecules and influence cellular processes. We describe how poor RNA aptamer expression and especially poor RNA aptamer folding have limited the use of RNA aptamers in RNA synthetic biology applications. We discuss innovative new approaches that promote RNA aptamer folding in living cells and how these approaches have improved the function of aptamers in mammalian cells. These new approaches are making RNA aptamer-based synthetic biology and RNA aptamer therapeutic applications much more achievable.
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Affiliation(s)
- Qian Hou
- Tri-Institutional PhD Program in Chemical Biology, Weill Cornell Medicine, The Rockefeller University, Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Department of Pharmacology, Weill Cornell Medical College, Cornell University, New York, NY, USA
| | - Samie R. Jaffrey
- Tri-Institutional PhD Program in Chemical Biology, Weill Cornell Medicine, The Rockefeller University, Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Department of Pharmacology, Weill Cornell Medical College, Cornell University, New York, NY, USA
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5
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Spinach-based RNA mimicking GFP in plant cells. Funct Integr Genomics 2022; 22:423-428. [PMID: 35267109 PMCID: PMC9197860 DOI: 10.1007/s10142-022-00835-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 02/16/2022] [Accepted: 02/16/2022] [Indexed: 12/23/2022]
Abstract
Spinach RNA-mimicking GFP (S-RMG) has been successfully used to monitor cellular RNAs including microRNAs in bacterium, yeast, and human cells. However, S-RMG has not been established in plants. In this study, we found that like bacterial, yeast, and human cellular tRNAs, plant tRNAs such as tRNALys can protect and/or stabilize the Spinach RNA aptamer interaction with the fluorophore DFHBI enabling detectable levels of green fluorescence to be emitted. The tRNALys-Spinach-tRNALys, once delivered into "chloroplast-free" onion epidermal cells can emit strong green fluorescence in the presence of DFHBI. Our results demonstrate for the first time that Spinach-based RNA visualization has the potential for in vivo monitoring of RNAs in plant cells.
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6
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Hyun Lee K, Kimoto M, Kawai G, Okamoto I, Fin A, Hirao I. Dye‐Conjugated Spinach RNA by Genetic Alphabet Expansion. Chemistry 2022; 28:e202104396. [DOI: 10.1002/chem.202104396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Indexed: 11/09/2022]
Affiliation(s)
- Kyung Hyun Lee
- Institute of Bioengineering and Bioimaging A*STAR 31 Biopolis Way, The Nanos #07-01 Singapore 138669 Singapore
| | - Michiko Kimoto
- Institute of Bioengineering and Bioimaging A*STAR 31 Biopolis Way, The Nanos #07-01 Singapore 138669 Singapore
| | - Gota Kawai
- Chiba Institute of Technology (CIT) Tsudanuma 2-17-1 Narashino Chiba 275-0016 Japan
| | - Itaru Okamoto
- Institute of Bioengineering and Bioimaging A*STAR 31 Biopolis Way, The Nanos #07-01 Singapore 138669 Singapore
| | - Andrea Fin
- Institute of Bioengineering and Bioimaging A*STAR 31 Biopolis Way, The Nanos #07-01 Singapore 138669 Singapore
| | - Ichiro Hirao
- Institute of Bioengineering and Bioimaging A*STAR 31 Biopolis Way, The Nanos #07-01 Singapore 138669 Singapore
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7
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Christopher JA, Geladaki A, Dawson CS, Vennard OL, Lilley KS. SUBCELLULAR TRANSCRIPTOMICS & PROTEOMICS: A COMPARATIVE METHODS REVIEW. Mol Cell Proteomics 2021; 21:100186. [PMID: 34922010 PMCID: PMC8864473 DOI: 10.1016/j.mcpro.2021.100186] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 11/16/2021] [Accepted: 12/13/2021] [Indexed: 12/23/2022] Open
Abstract
The internal environment of cells is molecularly crowded, which requires spatial organization via subcellular compartmentalization. These compartments harbor specific conditions for molecules to perform their biological functions, such as coordination of the cell cycle, cell survival, and growth. This compartmentalization is also not static, with molecules trafficking between these subcellular neighborhoods to carry out their functions. For example, some biomolecules are multifunctional, requiring an environment with differing conditions or interacting partners, and others traffic to export such molecules. Aberrant localization of proteins or RNA species has been linked to many pathological conditions, such as neurological, cancer, and pulmonary diseases. Differential expression studies in transcriptomics and proteomics are relatively common, but the majority have overlooked the importance of subcellular information. In addition, subcellular transcriptomics and proteomics data do not always colocate because of the biochemical processes that occur during and after translation, highlighting the complementary nature of these fields. In this review, we discuss and directly compare the current methods in spatial proteomics and transcriptomics, which include sequencing- and imaging-based strategies, to give the reader an overview of the current tools available. We also discuss current limitations of these strategies as well as future developments in the field of spatial -omics. Subcellular information of protein and RNA give insights into molecular function. This review discusses strategies available to measure subcellular information. Hybridization of methods shows promise for exploring the composition of organelles. Advances are aiding understanding of the organisation and dynamics of cells.
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Affiliation(s)
- Josie A Christopher
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK; Milner Therapeutics Institute, Jeffrey Cheah Biomedical Centre, Puddicombe Way, Cambridge, CB2 0AW, UK
| | - Aikaterini Geladaki
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK; Department of Genetics, University of Cambridge, 20 Downing Place, Cambridge, CB2 3EJ, UK
| | - Charlotte S Dawson
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK; Milner Therapeutics Institute, Jeffrey Cheah Biomedical Centre, Puddicombe Way, Cambridge, CB2 0AW, UK
| | - Owen L Vennard
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK; Milner Therapeutics Institute, Jeffrey Cheah Biomedical Centre, Puddicombe Way, Cambridge, CB2 0AW, UK
| | - Kathryn S Lilley
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK; Milner Therapeutics Institute, Jeffrey Cheah Biomedical Centre, Puddicombe Way, Cambridge, CB2 0AW, UK.
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8
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Li X, Wu J, Jaffrey SR. Engineering Fluorophore Recycling in a Fluorogenic RNA Aptamer. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202108338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Xing Li
- Beijing Institutes of Life Science Chinese Academy of Sciences Beijing 100101 P. R. China
- Department of Pharmacology Weill Cornell Medicine Cornell University New York NY 10065 USA
| | - Jiahui Wu
- Department of Pharmacology Weill Cornell Medicine Cornell University New York NY 10065 USA
| | - Samie R. Jaffrey
- Department of Pharmacology Weill Cornell Medicine Cornell University New York NY 10065 USA
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9
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Li X, Wu J, Jaffrey SR. Engineering Fluorophore Recycling in a Fluorogenic RNA Aptamer. Angew Chem Int Ed Engl 2021; 60:24153-24161. [PMID: 34490956 PMCID: PMC8661118 DOI: 10.1002/anie.202108338] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 07/27/2021] [Indexed: 12/13/2022]
Abstract
Fluorogenic aptamers can potentially show minimal photobleaching during continuous irradiation since any photobleached fluorophore can exchange with fluorescent dyes in the media. However, fluorophores have not been designed to maximize "fluorophore recycling." Here we describe TBI, a novel fluorophore for the Broccoli fluorogenic aptamer. Previous fluorophores either fail to rapidly dissociate when they undergo photobleaching via cis-trans isomerization, or bind slowly, resulting in extended periods after dissociation of the photobleached fluorophore when no fluorophore is bound. By contrast, photobleached TBI dissociates rapidly from Broccoli, and TBI from the media rapidly replaces dissociated photobleached fluorophore. Using TBI, Broccoli exhibits markedly enhanced fluorescence in cells during continuous imaging. These data show that designing fluorophores to optimize fluorophore recycling can lead to enhanced fluorescence of fluorogenic aptamers.
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Affiliation(s)
- Xing Li
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, 100101, P. R. China
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, NY, 10065, USA
| | - Jiahui Wu
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, NY, 10065, USA
| | - Samie R Jaffrey
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, NY, 10065, USA
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10
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Ryckelynck M. Development and Applications of Fluorogen/Light-Up RNA Aptamer Pairs for RNA Detection and More. Methods Mol Biol 2021; 2166:73-102. [PMID: 32710404 DOI: 10.1007/978-1-0716-0712-1_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The central role of RNA in living systems made it highly desirable to have noninvasive and sensitive technologies allowing for imaging the synthesis and the location of these molecules in living cells. This need motivated the development of small pro-fluorescent molecules called "fluorogens" that become fluorescent upon binding to genetically encodable RNAs called "light-up aptamers." Yet, the development of these fluorogen/light-up RNA pairs is a long and thorough process starting with the careful design of the fluorogen and pursued by the selection of a specific and efficient synthetic aptamer. This chapter summarizes the main design and the selection strategies used up to now prior to introducing the main pairs. Then, the vast application potential of these molecules for live-cell RNA imaging and other applications is presented and discussed.
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Affiliation(s)
- Michael Ryckelynck
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR 9002, Strasbourg, France.
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11
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Wang Y, Katanski CD, Watkins C, Pan JN, Dai Q, Jiang Z, Pan T. A high-throughput screening method for evolving a demethylase enzyme with improved and new functionalities. Nucleic Acids Res 2021; 49:e30. [PMID: 33337498 PMCID: PMC7968990 DOI: 10.1093/nar/gkaa1213] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 11/25/2020] [Accepted: 11/30/2020] [Indexed: 01/26/2023] Open
Abstract
AlkB is a DNA/RNA repair enzyme that removes base alkylations such as N1-methyladenosine (m1A) or N3-methylcytosine (m3C) from DNA and RNA. The AlkB enzyme has been used as a critical tool to facilitate tRNA sequencing and identification of mRNA modifications. As a tool, AlkB mutants with better reactivity and new functionalities are highly desired; however, previous identification of such AlkB mutants was based on the classical approach of targeted mutagenesis. Here, we introduce a high-throughput screening method to evaluate libraries of AlkB variants for demethylation activity on RNA and DNA substrates. This method is based on a fluorogenic RNA aptamer with an internal modified RNA/DNA residue which can block reverse transcription or introduce mutations leading to loss of fluorescence inherent in the cDNA product. Demethylation by an AlkB variant eliminates the blockage or mutation thereby restores the fluorescence signals. We applied our screening method to sites D135 and R210 in the Escherichia coli AlkB protein and identified a variant with improved activity beyond a previously known hyperactive mutant toward N1-methylguanosine (m1G) in RNA. We also applied our method to O6-methylguanosine (O6mG) modified DNA substrates and identified candidate AlkB variants with demethylating activity. Our study provides a high-throughput screening method for in vitro evolution of any demethylase enzyme.
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Affiliation(s)
- Yuru Wang
- Department of Biochemistry and Molecular Biology, USA.,Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | | | | | - Jessica N Pan
- Department of Biochemistry and Molecular Biology, USA
| | - Qing Dai
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Zhuoxun Jiang
- Department of Biochemistry and Molecular Biology, USA
| | - Tao Pan
- Department of Biochemistry and Molecular Biology, USA
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12
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Savage JC, Shinde P, Yao Y, Davare MA, Shinde U. A Broccoli aptamer chimera yields a fluorescent K + sensor spanning physiological concentrations. Chem Commun (Camb) 2021; 57:1344-1347. [PMID: 33432937 DOI: 10.1039/d0cc07042d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The RNA aptamer Broccoli accepts 2'fluorinated (2'F) pyrimidine nucleotide incorporation without perturbation of structure or fluorescence in the presence of potassium and DFHBI. However, the modification decreases Broccoli's apparent affinity for K+ >30-fold. A chimera of Broccoli RNAs with mixed chemistries displays linear fluorescent gain spanning physiological K+ concentrations, yielding an effective RNA-based fluorescent K+ sensor.
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Affiliation(s)
- Jonathan C Savage
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, USA.
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13
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Micura R, Höbartner C. Fundamental studies of functional nucleic acids: aptamers, riboswitches, ribozymes and DNAzymes. Chem Soc Rev 2020; 49:7331-7353. [PMID: 32944725 DOI: 10.1039/d0cs00617c] [Citation(s) in RCA: 96] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
This review aims at juxtaposing common versus distinct structural and functional strategies that are applied by aptamers, riboswitches, and ribozymes/DNAzymes. Focusing on recently discovered systems, we begin our analysis with small-molecule binding aptamers, with emphasis on in vitro-selected fluorogenic RNA aptamers and their different modes of ligand binding and fluorescence activation. Fundamental insights are much needed to advance RNA imaging probes for detection of exo- and endogenous RNA and for RNA process tracking. Secondly, we discuss the latest gene expression-regulating mRNA riboswitches that respond to the alarmone ppGpp, to PRPP, to NAD+, to adenosine and cytidine diphosphates, and to precursors of thiamine biosynthesis (HMP-PP), and we outline new subclasses of SAM and tetrahydrofolate-binding RNA regulators. Many riboswitches bind protein enzyme cofactors that, in principle, can catalyse a chemical reaction. For RNA, however, only one system (glmS ribozyme) has been identified in Nature thus far that utilizes a small molecule - glucosamine-6-phosphate - to participate directly in reaction catalysis (phosphodiester cleavage). We wonder why that is the case and what is to be done to reveal such likely existing cellular activities that could be more diverse than currently imagined. Thirdly, this brings us to the four latest small nucleolytic ribozymes termed twister, twister-sister, pistol, and hatchet as well as to in vitro selected DNA and RNA enzymes that promote new chemistry, mainly by exploiting their ability for RNA labelling and nucleoside modification recognition. Enormous progress in understanding the strategies of nucleic acids catalysts has been made by providing thorough structural fundaments (e.g. first structure of a DNAzyme, structures of ribozyme transition state mimics) in combination with functional assays and atomic mutagenesis.
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Affiliation(s)
- Ronald Micura
- Institute of Organic Chemistry and Center for Molecular Biosciences Innsbruck CMBI, Leopold-Franzens University Innsbruck, Innsbruck, Austria.
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14
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Li X, Mo L, Litke JL, Dey SK, Suter SR, Jaffrey SR. Imaging Intracellular S-Adenosyl Methionine Dynamics in Live Mammalian Cells with a Genetically Encoded Red Fluorescent RNA-Based Sensor. J Am Chem Soc 2020; 142:14117-14124. [PMID: 32698574 PMCID: PMC8158784 DOI: 10.1021/jacs.0c02931] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
To understand the role of intracellular metabolites in cellular processes, it is important to measure the dynamics and fluxes of small molecules in living cells. Although conventional metabolite sensors composed of fluorescent proteins have been made to detect some metabolites, an emerging approach is to use genetically encoded sensors composed of RNA. Because of the ability to rapidly generate metabolite-binding RNA aptamers, RNA-based sensors have the potential to be designed more readily than protein-based sensors. Numerous strategies have been developed to convert the green-fluorescent Spinach or Broccoli fluorogenic RNA aptamers into metabolite-regulated sensors. Nevertheless, red fluorescence is particularly desirable because of the low level of red background fluorescence in cells. However, the red fluorescent variant of the Broccoli aptamer, Red Broccoli, does not exhibit red fluorescence in cells when imaged with its cognate fluorophore. It is not known why Red Broccoli is fluorescent in vitro but not in live mammalian cells. Here, we develop a new fluorophore, OBI (3,5-difluoro-4-hydroxybenzylidene-imidazolinone-2-oxime-1-benzoimidazole), which binds Red Broccoli with high affinity and makes Red Broccoli resistant to thermal unfolding. We show that OBI enables Red Broccoli to be readily detected in live mammalian cells. Furthermore, we show that Red Broccoli can be fused to a S-adenosyl methionine (SAM)-binding aptamer to generate a red fluorescent RNA-based sensor that enables imaging of SAM in live mammalian cells. These results reveal a red fluorescent fluorogenic aptamer that functions in mammalian cells and that can be readily developed into red fluorescent RNA-based sensors.
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Affiliation(s)
- Xing Li
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
| | - Liuting Mo
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
| | - Jacob L Litke
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
| | - Sourav Kumar Dey
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
| | - Scott R Suter
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
| | - Samie R Jaffrey
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, New York 10065, United States
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15
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Steinmetzger C, Bessi I, Lenz AK, Höbartner C. Structure-fluorescence activation relationships of a large Stokes shift fluorogenic RNA aptamer. Nucleic Acids Res 2020; 47:11538-11550. [PMID: 31740962 PMCID: PMC7145527 DOI: 10.1093/nar/gkz1084] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 10/13/2019] [Accepted: 11/01/2019] [Indexed: 12/21/2022] Open
Abstract
The Chili RNA aptamer is a 52 nt long fluorogen-activating RNA aptamer (FLAP) that confers fluorescence to structurally diverse derivatives of fluorescent protein chromophores. A key feature of Chili is the formation of highly stable complexes with different ligands, which exhibit bright, highly Stokes-shifted fluorescence emission. In this work, we have analyzed the interactions between the Chili RNA and a family of conditionally fluorescent ligands using a variety of spectroscopic, calorimetric and biochemical techniques to reveal key structure–fluorescence activation relationships (SFARs). The ligands under investigation form two categories with emission maxima of ∼540 or ∼590 nm, respectively, and bind with affinities in the nanomolar to low-micromolar range. Isothermal titration calorimetry was used to elucidate the enthalpic and entropic contributions to binding affinity for a cationic ligand that is unique to the Chili aptamer. In addition to fluorescence activation, ligand binding was also observed by NMR spectroscopy, revealing characteristic signals for the formation of a G-quadruplex only upon ligand binding. These data shed light on the molecular features required and responsible for the large Stokes shift and the strong fluorescence enhancement of red and green emitting RNA–chromophore complexes.
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Affiliation(s)
- Christian Steinmetzger
- Institute of Organic Chemistry, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Irene Bessi
- Institute of Organic Chemistry, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Ann-Kathrin Lenz
- Institute of Organic Chemistry, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Claudia Höbartner
- Institute of Organic Chemistry, Julius-Maximilians-University Würzburg, Am Hubland, 97074 Würzburg, Germany
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16
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Saady A, Wojtyniak M, Varon E, Böttner V, Kinor N, Shav-Tal Y, Ducho C, Fischer B. Specific, Sensitive, and Quantitative Detection of HER-2 mRNA Breast Cancer Marker by Fluorescent Light-Up Hybridization Probes. Bioconjug Chem 2020; 31:1188-1198. [DOI: 10.1021/acs.bioconjchem.0c00130] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Abed Saady
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Melissa Wojtyniak
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, 66123 Saarbrücken, Germany
| | - Eli Varon
- Faculty of Life Sciences & Institute of Nanotechnology, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Verena Böttner
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, 66123 Saarbrücken, Germany
| | - Noa Kinor
- Faculty of Life Sciences & Institute of Nanotechnology, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Yaron Shav-Tal
- Faculty of Life Sciences & Institute of Nanotechnology, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Christian Ducho
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, 66123 Saarbrücken, Germany
| | - Bilha Fischer
- Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
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17
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Li X, Kim H, Litke JL, Wu J, Jaffrey SR. Fluorophore‐Promoted RNA Folding and Photostability Enables Imaging of Single Broccoli‐Tagged mRNAs in Live Mammalian Cells. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201914576] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Xing Li
- Department of PharmacologyWeill Cornell MedicineCornell University New York NY 10065 USA
| | - Hyaeyeong Kim
- Department of PharmacologyWeill Cornell MedicineCornell University New York NY 10065 USA
| | - Jacob L. Litke
- Department of PharmacologyWeill Cornell MedicineCornell University New York NY 10065 USA
| | - Jiahui Wu
- Department of PharmacologyWeill Cornell MedicineCornell University New York NY 10065 USA
| | - Samie R. Jaffrey
- Department of PharmacologyWeill Cornell MedicineCornell University New York NY 10065 USA
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18
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Savage JC, Davare MA, Shinde U. Subtle sequence variations alter tripartite complex kinetics and G-quadruplex dynamics in RNA aptamer Broccoli. Chem Commun (Camb) 2020; 56:2634-2637. [PMID: 32016232 DOI: 10.1039/c9cc09375c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Though extensively utilized, the fluorescent RNA aptamer Broccoli is poorly characterized with an unknown structure. Spectroscopic and kinetic investigations of tripartite complex formation reveal surprising differences between Broccoli and Spinach aptamers despite extreme sequence conservation. Our studies highlight how subtle sequence variations impart functional consequences of G-quadruplex-cation interactions in RNA.
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Affiliation(s)
- Jonathan C Savage
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, USA.
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19
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Li X, Kim H, Litke JL, Wu J, Jaffrey SR. Fluorophore-Promoted RNA Folding and Photostability Enables Imaging of Single Broccoli-Tagged mRNAs in Live Mammalian Cells. Angew Chem Int Ed Engl 2020; 59:4511-4518. [PMID: 31850609 DOI: 10.1002/anie.201914576] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Indexed: 11/11/2022]
Abstract
Spinach and Broccoli are fluorogenic RNA aptamers that bind DFHBI, a mimic of the chromophore in green fluorescent protein, and activate its fluorescence. Spinach/Broccoli-DFHBI complexes exhibit high fluorescence in vitro, but they exhibit lower fluorescence in mammalian cells. Here, computational screening was used to identify BI, a DFHBI derivative that binds Broccoli with higher affinity and leads to markedly higher fluorescence in cells compared to previous ligands. BI prevents thermal unfolding of Broccoli at 37 °C, leading to more folded Broccoli and thus more fluorescent Broccoli-BI complexes in cells. Broccoli-BI complexes are more photostable owing to impaired photoisomerization and rapid unbinding of photoisomerized cis-BI. These properties enable single mRNA containing 24 Broccoli aptamers to be imaged in live mammalian cells treated with BI. Small molecule ligands can thus promote RNA folding in cells, and thus allow single mRNA imaging with fluorogenic aptamers.
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Affiliation(s)
- Xing Li
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, NY, 10065, USA
| | - Hyaeyeong Kim
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, NY, 10065, USA
| | - Jacob L Litke
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, NY, 10065, USA
| | - Jiahui Wu
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, NY, 10065, USA
| | - Samie R Jaffrey
- Department of Pharmacology, Weill Cornell Medicine, Cornell University, New York, NY, 10065, USA
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20
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Truong L, Ferré-D'Amaré AR. From fluorescent proteins to fluorogenic RNAs: Tools for imaging cellular macromolecules. Protein Sci 2019; 28:1374-1386. [PMID: 31017335 DOI: 10.1002/pro.3632] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 04/23/2019] [Indexed: 01/01/2023]
Abstract
The explosion in genome-wide sequencing has revealed that noncoding RNAs are ubiquitous and highly conserved in biology. New molecular tools are needed for their study in live cells. Fluorescent RNA-small molecule complexes have emerged as powerful counterparts to fluorescent proteins, which are well established, universal tools in the study of proteins in cell biology. No naturally fluorescent RNAs are known; all current fluorescent RNA tags are in vitro evolved or engineered molecules that bind a conditionally fluorescent small molecule and turn on its fluorescence by up to 5000-fold. Structural analyses of several such fluorescence turn-on aptamers show that these compact (30-100 nucleotides) RNAs have diverse molecular architectures that can restrain their photoexcited fluorophores in their maximally fluorescent states, typically by stacking between planar nucleotide arrangements, such as G-quadruplexes, base triples, or base pairs. The diversity of fluorogenic RNAs as well as fluorophores that are cell permeable and bind weakly to endogenous cellular macromolecules has already produced RNA-fluorophore complexes that span the visual spectrum and are useful for tagging and visualizing RNAs in cells. Because the ligand binding sites of fluorogenic RNAs are not constrained by the need to autocatalytically generate fluorophores as are fluorescent proteins, they may offer more flexibility in molecular engineering to generate photophysical properties that are tailored to experimental needs.
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Affiliation(s)
- Lynda Truong
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, Bethesda, Maryland, 20892-8012
| | - Adrian R Ferré-D'Amaré
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, Bethesda, Maryland, 20892-8012
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